How can i fix my vauxhall vectra di(1995cc) 1999 reg?

there is an intermittent whining/buzzing noise coming from the front of my '99 vauxhall vectra turbo diesel di (1995CC) mileage 126,000 which increases when the accelerator pedal is pushed down.mpg is about 44 at present and engine performance is ok
Any advice please?